Tissue Development, Repair, and Remodeling - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 703

and JAMa interact with α L β 2 -integrin and form a ring-shaped cluster around the

leukocyte [ 1445 ]. Transcellular migration requires the supply of additional mem-
brane by the vacuolovesicular organelles to build a transcellular pore that lenghtens
toward the basal membrane. Both ICAM1 and caveolin-1 translocate toward the
transcellular pore. Membrane fusion is regulated by Ca 2 + and SNARE-containing
complexes [ 1445 ]. Intermediate filament constituent vimentin contributes to the
transcellular pore.

Selectins

The selectin family of transmembrane adhesion receptors mediates leukocyte teth-
ering and rolling. Selectin-P on endothelial cells is the primary adhesion molecule
for cell capture and rolling onto vascular endothelium. The main leukocyte ligand
for P-selectin is selectin-P ligand (SelPLg; a.k.a. P-selectin glycoprotein ligand-1
[PSGL1] and CD162). 33
Selectin-L also contributes significantly to leukocyte capture. Selectin-L and -
E also take part in rolling. Selectin-L is much less efficient than P-selectin in
cell rolling. Nonetheless, it is necessary to capture leukocytes and initiate their
rolling. Selectin-E may be responsible for slow rolling interactions and possibly
the initiation of firm adhesion.
Selectin-E and -P interact with L-selectin and PSGL1 expressed by leukocytes
(Table 11.7 ). In addition, E-selectin targets other specific ligands, such as E-selectin
ligand ESL1 (a.k.a. Golgi body sialoglycoprotein GlG1 and cysteine-rich fibroblast
growth factor receptor CFR1), epican (a.k.a. extracellular matrix receptor ECMR3,
GP90 lymphocyte homing-adhesion receptor, heparan sulfate proteoglycan recep-
tor, and CD44).

Integrins

β 2 Integrins participate in leukocyte deceleration and arrest. Neutrophils express
small amounts of other integrins such as α 4 β 1 -integrin that binds to endothelial

VCAM1 molecule. Integrin- α L β 2 is the most important integrin in firm leukocyte

adhesion, whereas α M β 2 -integrin seems to be important in neutrophil activation

and phagocytosis. Both α L β 2 -and α M β 2 -integrins can bind to ICAM1 and ICAM2

molecules.
Neutrophils and some lymphocyte subpopulations use preferentially α L β 2 -

integrin for firm adhesion. On the other hand, monocytes and lymphoblasts target
predominantly

α 4 β 1 -integrin [ 1445 ].

33 P-selectin glycoprotein ligand-1 on all lymphocytes, monocytes, eosinophils, and neutrophils
allows these cells to bind to endothelial P-selectin and, then, to roll along the endothelium.